Mechanisms of Ventilator-Induced Lung Injury (Part 1) See also Part 2: Prevention and Management of Ventilator-Induced Lung Injury Although invasive mechanical ventilation saves tens of thousands of lives each year, it can also be harmful, causing or worsening acute respiratory distress syndrome (ARDS) when misapplied. The repetitive stretching of lung tissue during positive pressure ventilation [… read more]
Mechanical Ventilation in ARDS Due to Sepsis See all PulmCCM reviews of: Surviving Sepsis Guidelines Sepsis is one of the main causes of acute respiratory distress syndrome (ARDS), in which the lungs are injured by circulating inflammatory mediators, resulting in severely impaired gas exchange usually requiring invasive mechanical ventilation. ARDS also results in poor lung [… read more]
Low Tidal Volume Ventilation Improves Outcomes in Elective Surgery Using low tidal volumes (6-8 mL/kg ideal body weight, or about 500 mL in the average man) during mechanical ventilation has been known for more than a decade to be lifesaving for people with acute respiratory distress syndrome (ARDS). Since reducing mortality by a relative 22% [… read more]
Prone Positioning Saves Lives in Severe ARDS Patients: NEJM It’s long been known that positioning patients with ARDS on mechanical ventilation face-down (prone) improves their oxygenation. (There are various theories why prone positioning helps, such as by reducing ARDS’s injurious heterogeneous alveolar overdistension.) The improved oxygen levels have never translated into improved outcomes in ARDS [… read more]
image: wikimedia Pulse Oximetry: The 30-Second Time Machine Why does it seem to take so long to re-oxygenate your crashing patient? Because your pulse oximeter is lying to you, no matter how good it is. Telescopes show us how a star looked millions or billions of years ago; pulse oximeters create a similar, though tiny [… read more]
In ARDS, Obesity May Protect Life (But Not Kidneys) by Blair Westerly, MD Obesity is an epidemic and common in intensive care units in the United States. Furthermore, while acute kidney injury (AKI) is also common in critically ill patients, obese patients carry additional risk for AKI because of increased baseline comorbidities. Both obesity and [… read more]
(image: Wikipedia) High-Frequency Oscillatory Ventilation (HFOV) for ARDS Two Randomized Trials: Early HFOV Doesn’t Help, May Harm High-frequency oscillatory ventilation (HFOV) has been proposed as a first-line therapy for acute respiratory distress syndrome (ARDS). By delivering 3-15 breaths per second of tiny tidal volumes (~70 mL), HFOV has appeal as the “ultimate” lung protective ventilator [… read more]
Low Tidal Volumes Improve Outcomes in Non-ARDS Patients Since the landmark ARDSnet trial of low tidal volume ventilation published in the NEJM in 2000, protecting the injured lung with low tidal volumes has been widely adopted. In case you missed it, that trial showed that low tidal volume ventilation (6 ml/kg IBW) improved mortality from [… read more]
In most areas of life, it helps to be tall, and needing treatment for ARDS further proves the rule. Tall people are less likely to get harmful lung-distending tidal volumes during mechanical ventilation, simply by virtue of having bigger lungs. It’s bad enough that we intensivists might discriminate against the under-six-feet crowd (of which I [… read more]
(image: Wikipedia) An expert panel announced a new definition and severity classfication system for acute respiratory distress syndrome (ARDS) that aims to simplify the diagnosis and better prognosticate outcomes from the life-threatening pulmonary illness. The proposed “Berlin definition of ARDS” predicted mortality ever-so-slightly better than the existing ARDS criteria (created at the 1994 American-European Consensus [… read more]
Where should we set the dial for caloric delivery to our patients with acute lung injury and acute respiratory distress syndrome (ARDS)? Weak observational trials suggest low caloric intake might be associated with poor outcomes [ref1, 2]. On the other hand, other observational data suggests just the opposite: restricting calories early on may reduce ventilator [… read more]
Human recombinant granulocyte macrophage colony stimulating factor (GM-CSF or Leukine) did not reduce ventilator-days in patients with acute lung injury / ARDS in a randomized trial published in the January 2012 Critical Care Medicine. Why would it have? Interestingly, patients with ARDS with higher levels of GM-CSF in their BAL fluid are more likely to survive. GM-CSF maintains [… read more]
Mechanical Ventilation in ARDS: Overview Mechanical ventilation in ARDS is almost always required, as people with acute respiratory distress syndrome are by definition severely hypoxemic. Yet mechanical ventilation itself can further injure damaged lungs(so-called ventilator induced lung injury); minimizing any additional damage while maintaining adequate gas exchange (“compatible with life”) is the central goal of mechanical [… read more]
It wasn’t such a crazy idea, injecting beta-agonists continuously into the veins of people with acute respiratory distress syndrome (ARDS) for a week. After all, if you spray some albuterol on alveolar epithelial cells in a dish, it upregulates their cAMP production and doubles the rate at which they clear fluid across their basement membranes. [… read more]
Numerous small (n~100), single-center randomized trials have shown a benefit of omega-3 fatty acids in acute lung injury and ARDS (reduced mortality, length of stay, and organ failure; improved oxygenation and respiratory mechanics). A meta-analysis combining these studies suggested a stat.significant benefit in mortality (risk ratio 0.67), ventilator requirement (-5 days), and ICU stay (-4 [… read more]
Daniel Brodie and Matthew Bacchetta offer a nice review of extracorporeal membrane oxygenation (ECMO) for acute respiratory distress syndrome (ARDS) in adults, based on their experience at Columbia University in New York City. This general overview describes ECMO techniques and re-visits the CESAR trial results — the only major randomized controlled trial on ECMO in ARDS [… read more]
In the longest longitudinal study of acute respiratory distress syndrome (ARDS) yet, Herridge et al followed 109 young survivors of severe ARDS (medians: age 44; Lung Injury Score 3.7 out of 4) in Canada for 5 years, enrolling 1998-2001. Twelve died in the first year. At 5 years, the survivors remained below their pre-ARDS exercise tolerance; they [… read more]
Obesity may impose extra burdens on critical care staff (think turning, transport, intubation and central line placement), but reviews suggest people with “ordinary” obesity (BMI 30-39) with have the same mortality from critical illness as overweight or healthy-weight people. In fact, obese people may have a survival advantage, despite possible longer durations of mechanical ventilation and ICU stays. But what about extreme obesity (BMI > [… read more]
October’s Seminars in Respiratory & Critical Care Medicine brings you 110 pages and 11 articles on organ failure in the intensive care unit, with articles including: Organ failure scoring and predictive models Cardiac alterations due to organ failure The microcirculation as a therapeutic target in shock Immuologic derangements in organ failure Acute lung failure Cardiogenic [… read more]
The 2009 randomized CESAR trial in Lancet concluded that in severe ARDS in the U.K., referral to an ECMO center saved lives. However, patients in the control (non-ECMO) group didn’t consistently get low-tidal ventilation, and many patients randomized to ECMO never received it, creating skepticism of the findings. A case series from Australia/New Zealand (ANZ ECMO) in JAMA showed a 70% survival [… read more]
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